Treatment of hydrocarbon oils



Patented Oct. 10, 1933 TREATMENT OF HYDROCARBON OILS I Harold G. Weber,Milton, Mass., assignor to Universal Oil Products Company, Chicago,111., a," corporation of South Dakota No Drawing. Application December10, 1931 o Serial No. 580,221

3 Claims. (01. 196-30) This invention relates to the treatment ofhydrocarbon oils and refers more particularly to the treatment of thelower boiling motor fuel fractions produced in the'straight rundistilla- "5 tion of crude petroleums or from cracking the heavierportions thereof.

More specifically the invention has reference to the methodof'treatme'nt of such low boiling motor fuel fractions to'reduoe theirtotal sulphur content, though other beneficial refining effects may beproduced at thesame time.

A limit has been placedonthe total sulphur allowable in minor'fuels forautomobile engines owing to the tendencyof sulphur compounds of certaintypes to corrode feed lines, carburetor parts, etc., and the tendency oftheseand other compounds to form traces of sulphuric acid when the fuelis burned in the engine, the acid leaking past the'piston ringssufficiently to cause some corrosion 'of the crank case. Since themajority of present day gasoline specifications have set a limit ofapproximately one-tenth of one percent as the maximum sulphur allowancein motor fuel, and since many straight run gasolines and the majority ofcracked gasolines contain sulphur in excess of this amount, it has beennecessary to devise treatments to reduce the sulphur content below theallowable limit.

The relative proportions of highly unsaturated or gum-forming compoundsand sulphur derivatives' in cracked gasolines or naphthas produced fromvarious charging stocks and under widely varying cracking plantoperations makes the treatmentof each individual distillate a specialproblem.

'In some cases the problem may be primarily i one of sulphur removal andin other cases, such as in the caseof distillates resulting-from thehigh temperature cracking of low sulphur charging stocks, the problemmay be rather the removal of the highly unsaturated olefinichydrocarbons. v I

It is usual to find in treatments for. desulphurization that the sulphurcontent may be reduced to a certain point with comparative ease, afterwhich reductions are effected with great difliculty owing to the form orcombination of the remaining sulphur, which apparently is contained inheterocycliccompounds, such as thio phene. The present invention isconcerned with an eflicient method of reducing the sulphur content ofcracked gasolines below the point usually attained by the presentcommercialtreating processes, though the treatment'may also beeffectively applied to the removal of the more easily reactive types ofsulphur compounds such as'free hydrogen sulphide, mercaptans, sulphureth'ers, etc. I 1 In one specific embodiment the invention comprisestreatment of hydrocarbon oils in the presence of silver, anelectro-positive metal and a solution of salts capable of producinghydroxyl and chloride'ions. v

It will be evident from the foregoing to those versed in the science ofelectro-chem-istry that under the conditions disclosed the particles-ofsilver and the electro-positive metals, which are preferably present ina finely divided condition, form an electric couple. The marked afiinityof silver for sulphur results in the rapid 'dissocia- 70. tion of thesulphur compounds with the fixation of sulphur on the surface of thesilverr The innumerable small cell units which constantly generatehydrogen ions then act upon-the'superficial layer of sulphide to formgaseous hydrogen sulphide and renew the surface of the silver forfurther action, so that the process of desulphurlzation may be madesubstantially continuous under properly regulated conditions; i Ofthe-electro-positive metals which maybe 30 used to form electric coupleswith the silver particles it is preferred to use those which arerelatively high in the electro-chemical series, and those which arecapable of being readilyproduced in a finely divided condition; Asmetals meeting these requirements maybem ention'ed sodium aluminum,zinc, cadmium,-iron,*etc.

As salts capable of giving hydroxyl ions may be mentioned the ordinarycaustic alkalis,'such as caustic soda, caustic potash, and thecarbonates and bicarbonates of the alkali metals and ammonia. Chlorideson the same basis may be used to furnish chloride ions,'whose essentialfunction isto prevent the precipitation offhydroxides such as those ofaluminum or iron,'which precipitation removes the metal from the sphereof the reaction and eliminates it as one of the members of the electriccouple.

The processof the invention may be applied to the desulphurizing ofgasolines and to the light hydrocarbon, distillates in a variety ofways. As one mode of operation finely divided silver may be produced onan inert carrier, such as pumice, by the common steps ofimpregnating-the pumice particles with a solution of the nitrate of themetal, igniting the nitrate at a minimum temperature to produce theoxide, and reducing the oxide (also at a minimum temperature "topreserve the activity of thereduced mctallyand protecting the reducedmaterial from oxidizing influences until it is ready for use.

Similarly the electro-positive metals essential to the process may beseparately produced in a finely comminuted state and the silver andelectro-positive metals mixed in proper molecular proportions. To themixture of metals a strong solution of sodium carbonate and sodiumchloride may be added to form a slurry or mud and the mass added to apressure vessel provided with a mechanical stirring device. The oil tobe treated is then added to the autoclave and heated to the propertemperature for the desulphurizing reactions with concurrent vigorousagitation.

The hydrogen sulphide produced and other fixed gases may be releasedintermittently or continuously to keep the pressure within safe limits.'

At the conclusion of the treating period the agitation may be stoppedand the contents of the pressure vessel allowed to stratify, whereuponthe, upper layer of gasoline or naphtha may be removed and distilled inseparate equipment, partly by its contained heat, to produce an endpointproduct needing only caustic washing to remove traces of dissolvedhydrogen sulphide. I

The treating mass remaining in the pressure vessel may be used withoutfurther additions of metals or salts until its efilciency drops below aneconomical point, whereupon it may be renewed by well known chemicalmethods, involving water extraction of the mass to remove soluble saltsand the further extraction by acids or alkalis of the metallicparticles, and a repetition of the stepswhich produce them in thefinely'divided condition necessary for their effective electrochemicalaction.

Another mode of operation which is frequently convenient when dealingwith vapors arising from fractionators of crude stills or a crackingplant is to pass the vapors in a continuous stream upwardly through the.silver and electro-positive metals supported on the inert carrierscounter flow to the electrolyte salt solutions, concentration of thesolutions and the temperature and pressure of operation being soregulated that there is at all times an.aqueous electrolyte in contactwith the metallic particles. To provide against the contingency ofover-concentration ot the solution with resultant precipitation of Psalts possible clogging of the apparatus steam may be introduced intothe oil vapors undergoing treatment, the efiect of this addition beingto depress vaporization of the solvent.

' Operators skilled in the art of treating hydrocarbons will be able todevise other forms of equipment adaptable for producing the resultsdesired by the use of the process of the invention,

and since the invention is not limited to any form of apparatus in'whichit may be conducted it will be unnecessary to suggest further types.

As an example of the results obtainable when employing the process ofthe invention to treat gasoline vapors from' a cracking plant, a caseinvolving the use of a Mid-Continent gas oil as charging stock to thecracking plant may be cited. The cracking plant may be provided with afractionator of suflicient capacity to produce vapors of approximategasoline boiling point range at a pressureof '75 pounds per square inchand a top tower temperature of 400 -F., which temperature correspondsroughly to the end boiling point of the finished gasoline. The gasolineproduced without chemical treatmentof the vapors in such a case may havethe properties shown in the first column of the appended tabulation,these properties being shown in comparison with those of a gasoline madeby interposing the treating step characteristic of the present inventionas one stage in the fractionation of the gasoline. The details of theoperation may be essentially those already described in connection withvapor phase treatment, the solutions of mixed sodium bicarbonate andchloride being substantially saturated under the conditions of operationand used at the rate of 10 pounds of solution per barrel of condensedgasoline.

Untreated Treated gasoline gasoline Gravity A. P. I 54. 5 54. 8 EndpointF. 405 406 Color '(Saybolt) 8 +30 Color after 4 hrs. exposure tosunlight 25 Gums by copper dish 350 mgs 35 mgs. Total sulphur O. 3 0. 04

It may be possible to utilize the mixture of silver and aluminumcontinuously until an amount of gasolineeq'ual to10,000 barrels pertonof metal mixture has passed through the treater before anyr'evivification is necessary to maintain the efiiciency of the process.

As another example of results obtainable, a pressure distillate producedby cracking 2. Cali-- fornia. residuum may be treated by the batchmethod, as described in the specification; By using approximately doublethe amount of electrolyte (that .is 20 pounds per barrel) that was usedin the first example and treating for 15 to 20 minutes at a temperatureof 3'OO''F'. and a pressureof 200 pounds per square inch, the pressuredistillate maybe redistilled'to produce a finished gasoline needing onlya light causticwash to ren der it in a stable andmarketable condition;The tabulation following again shows the relative properties of thegasoline practiced by simple fractionationof the pressure'distilla'teand that produced by. fractionation of the treated distillate: f v

I It will be evident fro'mthe foregoing descrip'-- tion of the inventionand the examples of results obtainable by its use that the presentinvention furnishes an entirely practical and highly efii'cient methodfor the treatment of cracked distillates; However, since many otherexamples of operation and results might be given, andsince the processis also well adapted to the treatment or straight run distillates toproduce results sub-' stantially equivalentto those given in theexamples of use on cracked distillates, it is not intended that theforegoing specification shall act in a limitingsense upon the broadscope of the inven-' tion. r a

I claim as my invention:

- 1. A process for the refining of hydrocarbon distillates todesulphurize the same comprising subjecting the distillates to thesimultaneous ac- 3. A process for the refining of hydrocarbondistillates to desulphurize the same comprising subjecting thedistillates to the simultaneous action of aqueous solutions of sodiumbicarbonate and sodium chloride while in the presence of metallicsilver, and aluminum.

HAROLD C. WEBER.

